Thermal relay



Dec. 28, 1926.

H. D. HINELINE ET AL THERMAL RELAY Filed March 5. 1923 iNVENTORS y l ius.

ATTORNEY f l l /ll/ I 111// Wol-fer G. M

Harris D. Hrleline WITNESSES:

Fig. 1.

Patented Dec. 28, 1926.

UNITED STATES PATENT OFFICE.

ARRIS D. HINELINE, F PITTSBURGH, AND WALTER G. MYLIUS, OF WILKINSBURG, PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION 0F :.PENNS'YLVANIA.

THERMAL RELAY.

Application led March 5, 1923. Serial No. 622,795.

Our invention relates to electrical protective devices and more particularly to thermal relays.

One object of our invention is to provide a thermal relay that shall have suflicient time interval in the operation thereof to ei'ect protection of electrical apparatus from cverloads.

Another object of our invention is to prof vide a relay of the above-indicated character that shall employ a bimetallic element of such shape that a relatively great degree off .i heat and, consequently, a relatively large torque, may be developed therein.

Another object of4 our invention is to provide a relay, of the above-indicated character, that shall be simple and economical in construction and reliable in operation.

Heretofore, considerable difficulty has been encountered in developing suicient heat in a small bimetallic Ielement because the resistance of the element was too small to obtain ltorque of the required value.

In view of the difficulty of developing suilicient heat in a bimetallic element ot' the usual type heretofore used, we provide an element that corresponds in overall dimensions to those previously employed, but which is so slotted as to develop a currentconducting path greatly exceeding in length the former'current-conducting paths.

By reason of the shape otthe bimetallic element, the length of the current-conducting path in each stripis greatly increased in proportion to the lineal length of the strip, and by the disposition of the several strips in either series or parallel connec' tion a considerable electrical-conducting path is confined in a minimum cubical area, thereby greatly multiplying the effective re-4 sistance of the bimetallic element. The total heat and, consequently, the torque developed, are correspondingly increased.

Figure 1 is a longitudinal sectional view of a thermal relay embodying our inven? tion. v

Fig. 2 is a similar view taken at right angles thereto.

Fig. 3 is a cross-sectional view of the ther- IBnal relay taken along` the line III-III of iv. 1. Eig. 4 is a detail thereof.

`17, is a bimetallic element v18.

Fig. 5 is a diagrammatic illustration of electrical circuits and apparatus embodying our invention. In the ypreferred form of our invention, a cylindrical member 1 of non-conducting Ymaterial has its opposite ends closed by metallic caps 2 and 3 comprising metallic ferrules 4 and 5 respectively. Binding posts 6 and 7, in the form of clamping screws, extend through the caps 2 and 3,`

respectively, and also serve as securing means for brackets 8 and 9, respectively.

Bracket 9 comprises a main body portion 11 extending longitudinally of the cylinder l, an end portion l2 at a-right angle thereto engagingbinding post 7, and an end portion 13 at aslight angle to the main body portion 11. Secured to the body portion 11 is an electrical conductor 14 which extends through ca member 3, but is insulated therefrom as is s iown in Fig. 1. Conductor 14 is provided with a binding post 15. As is shown in Fig. 4, members 11 and 14 are secured together by rivets 16 and insulating material in such manner that no electrical connection exists between them.

Secured to the end portion 13 of bracket 9 and to the Abracket 8 by means of rivets The details of this connection are shown in F ig. 3, wherein a plurality of bimetallic strips 21 to 26 are shown held yin mechanical connection to one another and to members 8 and 9, ,by the rivets 17. Between each pair of bimetallic strips there is placed a layer of insulating material, and similar insulating .material is placed between certain portions 0f brackets 8 and 9 and the adjacent bimetallic strips 21 and 26, respectively, as is shown in Fig. 3.

The free end of the bimetallic element 18 is slightly offset, as at 27, into parallel re- A contact member 28 is mounted on the face of bimetallic member 18 adjacent'.v to

the portion 11, but not in electrical contact therewith and is soldered, over one half of its surface, to the member 18,` the other half of its surface being insulated there from. A contact member 29 is adjustably secured to the conductor 14 and' passes through; an enlarged opening 31y in the, body portion 11 without contact therewith. 4An opening 32 is provided in the cylinder 1 for adjustment of the contact member 29.

In operation, we place our relay in suitable clips (not shown) in the electrical circuit to be protected. Electrical contact is made between these clips and the ferrules y4 and 5. Considering the ferrule 4 to be the positive terminal, electrical current traverses a portion of the cap member 2, binding post 6, bracket 8 and the bimetallic strip 2l soldered to the bracket 8, as is shown at the right hand side of Fig. 3.

It is to be noted that the middle and lefthand sections of the strip 2l are insulated -from the bracket member f8. Current then traverses the several loops of the bimetallic strip, shown in Fig. 2, reaching the end of the strip 21. as shown at the left-hand side of Fig. 3, where soldered connection is made with the. nextbimetallic strip 22. It is "to be observed 'that strips 21 and 22 are insulated from one another at all other points on their surfaces. Current then traverses the strip 22 in a direction opposite to that taken in traversing the strip 21, andv at length reaches the end shown at the right of Fig. 3, where a soldered connection is made to the strip 23. This alternating connection between the bimetallic strips is repeated .until the current reaches bimetallic strip 26 which has a soldered connection to member 9, shown at the right of Fig. 3. Strip 26 is insulated from the member 9 at its middle and left-hand sections.

Current then traverses portion 13 and 11 of bracket 9, the binding post 7, the cap 3, and f' ferrule 5. It will be seen that normally no current traverses the'member 14 and that appreciable space exists between members 11 and 18 by/reason of the slight offset of the end 13.

- It is obvious that a arallel electrical connection may be had t rough the bimetallic member 18 by omitting the insulation between the several strips, or by soldering the several ends of these strips on both sides of Fig. 3, rather than in the stagger relationship shown.

Upon the occurrence of an excessive current in the bimetallic strip 18, a large amount of heat will be liberated. This heat will cause the member 18 to be deflected or buckeled in a predetermined direction. Contact member 29 is adjusted to engage contact member 28 upon a predetermined amount of deflection of the bimetallic element 18. Upon the closingr of these Contact members, electrical Contact is made between thestrip 26 of the bimetallic element and conductor 14.

In Fig. 5, we have shown a motorM re- -ceiving current through a circuitl 33, comprising our thermal relay R and a circuit interrupter 34, from a source of electromotire force Ze prefer to connect our tected, although it may be connected in shunt circuit with such device when desired..

Upon the closin of contact members 28 and 29, as hereto ore described, an electrical circuit 35, connected to the binding post 15, is energized. This circuitvcontrols a tripping mechanism 36 for the circuit interrupter 34, which is accordingly brought to the open circuit position, thereby interrupting the electrical circuit comprising the device M. y

It is thus seen that we have devised a thermal relay which is simple to construct, which has minimum number of parts, and which is rugged and adapted for hard usage.

Although we have shown one form of relay embodying a slotted bimeta'llic element, we do notulimit the element to the particular mode of'slotting that is illustrated, or to a relay embodying an element having the particular arrangement that is illustrated, as various modifications may be made-therein Withinthe spirit Aand scope ofthe invention as set forth in the appended claims.

We claim as our invention:

1. In a thermal relay, a thermo-responsive element comprising a plurality of bimetallic Strips, said strips havmg electric-insulating material inserted between each pair of adjacent bimetallic strips, means for electrically connecting each bimetallic strip'to the adjacent bimetallic strips at opposite edges thereof, and a singleelectrical connection to each of the outer bimetallic strips.

2. In a thermal relay, a thermo-responsive element comprising a plurality of strips of bimetal, each of said bimetallic strips having at least an electrical length of substantially twice its linear length, electric-insulating material inserted between each pair of adjacent bimetallic strips, each bimetallic strip being electrically connected to the ad jacent bimetallic strips, a single connection being so made at each end of said bimetallic strips that 'electrical connection through the bimetallic strips of said thermo-responsive element is secured.

3. In a thermal relay, a cylindrical body member, end members for said cylindrical member comprising metallic ferrules` a rigid mechanical means comprising a portion of a bimetallic element connecting said ferrules, said mechanical connecting element comprising a normal electrical connection between Said end members.

4. In a thermal relay, a cylindrical body member. end members for said cylindrical member comprisingfmetallic ferrules. a rigid mechanical means comprising a portion of a bimetallic element connecting said ferrules, said mechanical connecting means comprising a vnormal electrical connection between said end members, and a conductor extending through one of said end members mechanically carried by said mechanical connecting means. and means for closing an electrlcal `circuit between said conductor and said bimetallic element under predetermined conditions.

an opening in said end portion and means for completing an electrical circuit between said bimetallic element and the second metallic member under predetermined conditions.

6. In a cartridge type thermal relay, a body portion, a metallic member secured to one end of said body portion, a bimetallic element connected to said metallic member, a second metallic member mechanically secured to and electrically insulated from said metallic Amember and passing through an opening in said end portion and means` cornprising a contact member mounted on said second metallic member and extending through an opening` in the first named lnetallic member, for completing an electrical circuit between said bimetallic element and the secondpmetallic member under predetermined conditions in this bimetallic member.

7. In a thermal relay of the cartridge type, a body member, metallic end pieces therefor, a mechanical and electrical connection between said end pieces comprising a metallic bracket secured to one end piece and extending adjacent the other end piece, a second bracket member mounted on the other end piece at one side of the end of the rst named bracket, a bimetallic element disposed between said brackets, and means for securing said brackets and said bimetallic element together.

8. In a thermal relay of the cartridge type, a body member, metallic end pieces therefor, a mechanical and electrical connection between said end pieces comprising a metallic .bracket secured to one end piece and extending adjacent to the other end piece and terminating in a bent portion. a second bracket member mounted on the other end piece at one side of the end of the first named bracket, a bimetallic element so disposed between said brackets'and extending in substantially the plane of said bent portion that a space exists between the vtree end of said bimetallic element and the major portion of the first named bracket, and means for securing said brackets and said bimetallic element together.

yIn testimony whereof, We have hereunto subscribed our names this 24th day of February` 1923.

HARRIS D. HINELINE. WALTER G. MYLIUS. 

